Citizen of the Galaxy

Citizen of the Galaxy ran in Astounding Science Fiction across four issues in 1957 and came out in hardcover the same year as one of the Heinlein juveniles. The story owes a good deal to Rudyard Kipling's Kim.

The future of the book has interstellar flight and several alien races to trade with, but slavery has reappeared on some planets, and the military force of the human government spends much of its time trying to suppress the trade. Thorby is a defiant boy bought for almost nothing on the planet Jubbul, at a slave auction, by an old beggar called Baslim the Cripple.

Baslim takes him to an underground home that is much better appointed than it looks from outside, and raises him as a son, teaching him the trade of begging along with mathematics, history and several languages, and sending him on errands across the city. As Thorby grows up and begins to ask questions, the book turns into an inquiry into where he came from and what kind of citizen he means to be.